18. Given the electric network shown in Figure P1.6. [Review] a. Write the differential equation for the network if v(t) = u(t), a unit step. b. Solve the differential equation for the current, i(t), if there is no initial energy in the network. c. Make a plot of your solution if R/L = 1. R w v(t) i(t) 0000 L FIGURE P1.6 RL network