13. A cascade connection of two voltage amplifiers A1 and A2 is shown in the figure. The openloop gain Av0, input resistance Rin, and output resistance RO for A1 and A2 are as follows:
A1:Av0 =10Ω,Rin=10kΩ ,R0=1kΩ
A2: Av0 =5Ω,R=5kΩ , R=200Ω
The approximate overall voltage gain Vout /Vin is __________.