Mr. Santos signs up for a plan in which he is offered a discounted rate for cable service for four months. After this period, the cost will be an additional $5 per month. His total cost for cable service for the first year will be $304. Use the equation below to determine the discounted rate Mr. Santos will pay each month for the first four months.
4(x) + 8(x+5) = 304

a- $24
b- $18
c- $25
d- $22