a smartphone plan has a monthly base fee that includes 5 gigabytes of data. An overage charge is applied when the data usage exceeds 5 gigabytes. The equation C= 59 + 15(g-5) models the plan, where C represents the monthly cost, in dollars, and g represents the total number of gigabytes used for the month what does the value 15 represents in the equation?
a ) The base fee per month, in dollars, for the plan

b) the cost, in dollars, for each additional gigabyte used.

c) The average cost, in dollars, for data usage per month.

d) The average data usage, in gigabytes, per month.