12 what am I doing wrong here?

A painting firm contracts to paint the exterior of a larger water tank in the shape of a half-dome (a hemisphere) The radius of the tank is measured to be 100 It with a tolerance of +6 in. (+0 5 f) (The formula for surface area of a hemisphere is A=2ar"; use 3.14 as an approximation for x ] Each can of paint costs $30 and covers 200 It a) Calculate dA, the approximate difference in the burface area dun to the tolerance. b) Assuming the painters cannot bring partial carrs of paint to the job, how many extra cans should they bring to cover the extra area they may encounter? c) How much extra should the painters plan to spend on paint to account for the possible extra area? al dA = 320 (Simplify your answer.) bj The painters should bring 2 extra cans of paint to cover the extra area (Round up to the nearest intogar.) c) The painters should plan to spend $ 57 for the possible extra area. (Simplify your answer.)