Skill Level Rank Bonus Calculation (Finalized)

def skill_level(rank, difficulty):
    '''
    RANK += RANK BONUS PER RANK
    --------------------------
    1 to 10 += 3
    11 to 30 += 2
    31 to 50 += 1
    51 to 100 += 0.5
    101 to 150 += 0.25
    151 to 200 += 0.125
    201 to 500 += 0.0625
    501 to 1,000 += 0.025
    1,001 to infinity += 0.01
    '''
    #Temp Values
    rb = 0
    rank = 100

    #Formula
    if rank:
        r = rank if rank < 10 else 10
        rb += (3 * r)
        if rank >= 11:
            r = rank - 10 if rank < 30 else 10
            rb += (2 * r)
            if rank >= 31:
                r = rank - 30 if rank < 50 else 20
                rb += (1 * r)
                if rank >= 51:
                    r = rank - 50 if rank < 100 else 50
                    rb += (0.5 * r)
                    if rank >= 101:
                        r = rank - 100 if rank < 150 else 50
                        rb += (0.25 * r)
                        if rank >= 151:
                            r = rank - 150 if rank < 200 else 50
                            rb += (0.125 * r)
                            if rank >= 201:
                                r = rank - 200 if rank < 500 else 300
                                rb += (0.0625 * r)
                                if rank >= 501:
                                    r = rank - 500 if rank < 1000 else 500
                                    rb += (0.025 * r)
                                    if rank >= 1001:
                                        r = rank - 1000
                                        rb += (0.01 * r)
        '''
        15% RB loss per difficulty.
        At rank 100:
        Easy(100%) 115 RB
        Average(85%) 97.75 RB
        Difficult(70%) 80.5 RB
        Impossible(55%) 63.25 RB
        '''
        if difficulty == 'easy':
            rb *= 1
        elif difficulty == 'average':
            rb *= 0.85
        elif difficulty == 'difficult':
            rb *= 0.7
        elif difficulty == 'impossible':
            rb *= 0.55
        return rb # Return if any rank.
    return None # Return if no rank.