Answer:
32.76 Volt
Step-by-step explanation:
frequency, f = 400 Hz
Area of crossection, A = 13 cm²
Maximum flux density, B = 0.9 tesla 
Number of turns in secondary coil, N = 70 
Let the maximum induced voltage is e.
According to the Faraday's law of electromagnetic induction, the induced emf is equal to the rate of change of magnetic flux. 
e = dФ/dt 

Time is defined as the reciprocal of frequency. 
So, e = N B A f 
e = 70 x 0.9 x 13 x 10^-4 x 400 
e = 32.76 volt