Is there a picture of the circle for this question?
First you find the probability of each coin turning up tails, then you multiply the two probabilities together:
1/2 x 1/2 = 1/4
S(p)= 5(12)= $60
D(p)= 120-4(12)= $72
459.6 - 150 = 309.6
309.6 / 12 = $25.80 a month for 12 months