Sandra is selling brownies to save money for the French Club. The equation \( f(x) = 0.5x - 10 \) represents her profit, \( f(x) \), for selling \( x \) brownies. Which statement is true about the value of \( f(78) \)?

A. The value \( f(78) = 29 \) and it represents a profit of 29 dollars after selling 78 brownies.

B. The value \( f(78) = 29 \) and it represents a profit of 78 dollars after selling 29 brownies.

C. The value \( f(78) = 49 \) and it represents a profit of 49 dollars after selling 78 brownies.

D. The value \( f(78) = 49 \) and it represents a profit of 78 dollars after selling 49 brownies.