Which function, C(x), represents the monthly cost in dollars in terms of x, the number of gigabytes used in a month?
C(x) = StartLayout enlarged left-brace 1st Row 1st column 15, 2nd column 0 less-than-or-equal-to x less-than-or-equal-to 2 2nd Row 1st column 5 x + 10, 2nd column 2 less-than x less-than-or-equal-to 6 3rd Row 1st column 50, 2nd column 6 less-than x EndLayout
C(x) = StartLayout enlarged left-brace 1st Row 1st column 15, 2nd column 0 less-than-or-equal-to x less-than 2 2nd Row 1st column 5 x + 20, 2nd column 2 less-than-or-equal-to x less-than 6 3rd Row 1st column 50, 2nd column 6 less-than-or-equal-to x EndLayout
C(x) = StartLayout enlarged left-brace 1st Row 1st column 15x, 2nd column 0 less-than-or-equal-to x less-than-or-equal-to 2 2nd Row 1st column 20 x + 5, 2nd column 2 less-than x less-than-or-equal-to 6 3rd Row 1st column 50 x, 2nd column 6 less-than x EndLayout
C(x) = StartLayout enlarged left-brace 1st Row 1st column 15x, 2nd column 0 less-than-or-equal-to x less-than 2 2nd Row 1st column 5 x + 10, 2nd column 2 less-than-or-equal-to x less-than 6 3rd Row 1st column 50 x, 2nd column 6 less-than-or-equal-to x EndLayout