prison rank up error log

[12:48:23] [Server thread/ERROR]: null
org.bukkit.command.CommandException: Unhandled exception executing command 'rankup' in plugin PrisonRankup v2.5
    at org.bukkit.command.PluginCommand.execute(PluginCommand.java:46) ~[craftbukkit.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:180) ~[craftbukkit.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at org.bukkit.craftbukkit.v1_7_R3.CraftServer.dispatchCommand(CraftServer.java:701) ~[craftbukkit.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.PlayerConnection.handleCommand(PlayerConnection.java:956) [craftbukkit.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.PlayerConnection.a(PlayerConnection.java:817) [craftbukkit.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.PacketPlayInChat.a(PacketPlayInChat.java:28) [craftbukkit.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.PacketPlayInChat.handle(PacketPlayInChat.java:47) [craftbukkit.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.NetworkManager.a(NetworkManager.java:157) [craftbukkit.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.ServerConnection.c(SourceFile:134) [craftbukkit.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.MinecraftServer.v(MinecraftServer.java:667) [craftbukkit.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.DedicatedServer.v(DedicatedServer.java:260) [craftbukkit.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.MinecraftServer.u(MinecraftServer.java:558) [craftbukkit.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.MinecraftServer.run(MinecraftServer.java:469) [craftbukkit.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    at net.minecraft.server.v1_7_R3.ThreadServerApplication.run(SourceFile:628) [craftbukkit.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
Caused by: java.lang.NoSuchMethodError: net.milkbowl.vault.economy.Economy.getBalance(Lorg/bukkit/OfflinePlayer;)D
    at net.craftservers.prisonrankup.Models.PRPlayer.canRankup(PRPlayer.java:135) ~[?:?]
    at net.craftservers.prisonrankup.SubCommands.Rankup.onCommand(Rankup.java:30) ~[?:?]
    at net.craftservers.prisonrankup.Models.CommandHandler.onCommand(CommandHandler.java:42) ~[?:?]
    at org.bukkit.command.PluginCommand.execute(PluginCommand.java:44) ~[craftbukkit.jar:git-Bukkit-1.7.9-R0.1-10-g8688bd4-b3092jnks]
    ... 13 more