Ahot air balloon resting on the ground has a 770 n lift force. the weight of the basket is 150 n, and the balloon plus the gas in it weigh 80 n. if a rider weighing 560 n gets in, which statement is correct?

a. the net force on the balloon is 20 n upward.
b. the net force on the balloon is 790 n upward.
c. the total weight of the balloon is 790 n upward.
d. the normal force of the ground on the balloon is 20 n upward.

i've can't find the solution to this problem, and i really need some on it. i honestly don't think there is a correct answer, but if someone could explain it to me i'd be pretty grateful.