#15

Read 4.5.
4.4; 41, 48, 60 as below, 67.
4.5; 7, 14, 16, 23, 37, 57.
Hints on 4.4; 48:  You may use calculator graph (y1(x) for V(t)) or Desmos to answer a,c,e.  On c, may find intersection with y=0.5.  On e, get value from graph (V'(240) in Desmos) but try symbolic derivative for practice (evaluation optional).
On 4.4; 60: Just find I' for r=4,n=3, but leave the rest of the constants as letters; you don't have to do parts a and b.  This prepares you for the evaluations of parts a and b, but these are OPTIONAL and most easily done by typing the formula into some computing (TI-89 or Desmos) where you can specify constants (b=8) and evaluate at points.