9. Greg needs at least $1.60 in stamps to mail a package. He has 28¢ and 4¢ stamps. He can use no more than twenty 4¢ stamps as he only has one book left. a) Write a system of linear inequalities to represent this situation, then graph.
b) Using your graph, give two possible combinations of stamps that Greg can use to ensure he mails his package with the correct postage.

Ahigh-altitude spherical weather balloon expands as it rises, due to the drop in atmospheric pressure. suppose that the radius r increases at the rate of 0.02 inches per second, and that r = 36 inches at time t = 0. determine the equation that models the volume v of the balloon at time t, and find the volume when t = 360 seconds. v(t) = 4π(0.02t)2; 651.44 in3 v(t) = 4π(36 + 0.02t)2; 1,694,397.14 in3 v(t) = four pi times the product of zero point zero two and t to the third power divided by three.; 4,690.37 in3 v(t) = four pi times the quantity of thirty six plus zero point zero two t to the third power divided by three.; 337,706.83 in3