Karina uses the system of equations below to compare the monthly utility costs in july and december for electricity, x, and natural gas, y.

750x + 17y = 141.61
300x + 30y = 75.90
karina solves the system using linear combination and arrives at the equation 116y = 96.28. she then solves this equation for y. which statement explains karina’s solution?

a. the cost of electricity is $0.17 per unit.
b. the cost of natural gas is $0.20 per unit.
c. the cost of electricity is $0.72 per unit.
d. the cost of natural gas is $0.83 per unit.