Transceiver system problem

[rockster]

Could someone help me with this problem please, im new to electronics

the problem:
You are required to design a transceiver system to send and receive an ‘on-off’ keyed (OOK) 40KHz signal using ultrasonic transducers.

The transmitted ultrasonic carrier frequency will be 40kHz. The modulation generated in the transmitter will switch every 80ms between 100Hz and 200Hz square waves. This modulation signal will then be used to switch the 40KHz carrier on and off, hence generating the OOK signal for transmission via the transducer.

The receiver will be designed to detect this signal at maximum achievable range and provide a demodulated audio output (alternate 100Hz and 200Hz tones) capable of being heard using standard 100 mW headphones.

Would i be right in saying that a 741 amplifier should be used?

Thanks