Any help with these 3 calc questions will be appreciated!

The link to the chart is below:

media. cheggcdn. com /media/a86/ a86f85b4-821e-4c06-863d-126b863efda e/ phpwYmomy

A. The radius of Balloon A is 5 feet when t=4 minutes. Estimate the radius of the balloon when t=4.5, using the tangent line approximation at t=4. It is known that the graph of r is concave down for the time 0

B. Balloon B has been removed from service and the radius of the balloon is decreasing at a rate of 2/pi feet per second. Find the rate at which the volume is decreasing when the radius of Balloon B is 2 feet.

C. The cost to maintain inventory for the weather balloons is given by C(x)=21,000/x + 2.4x, where x is the number of balloons in inventory. Find the marginal cost for adding the 101st balloon to the inventory. Explain the meaning of this extra balloon in context to the scenario