The atmospheric pressure, P = f(y, t) = (950+2t)e^−y∕7, in millibars, on a weather balloon, is a function of its height y ≥ 0, in km above sea level after t hours with 0 ≤ t ≤ 48.

Graph the following single-variable functions and explain the significance of the shape of the graph in terms of atmospheric pressure.

(a) f(3, t) 

(b) f(y, 24)