The answer is C, your b in the equation is 4, and your slope is 1/2. Starting from four, you move up one and right two which means the slope is 1/2.
1 quarter = 25 cents (he has 2 therefore its 50 cents)
10 dimes = 100 cents = 1 dollar
Oliver has twice as many dimes than he does quarters because 100 divided by 50 = 2. Hope this helps!