mnk = function(x,y) {
  n = length(x)
  sumxy = sum(x*y)
  sumx = sum(x)
  sumy = sum(y)
  sumxx = sum(x*x)
  sumsumx = sumx * sumx
  a = (n * sumxy - sumx * sumy)/(n*sumxx - sumsumx)
  b = sumy/n - a*sumx/n
  print(paste("a=",a," b=",b))
  plot(x,y)
  abline(b,a)
}
x = c(165, 170, 175, 180,185)
y = c(215, 227, 239, 250, 256)
mnk(x,y)