In a digital communication system employing Frequency Shift Keying $\text{(FSK)}$, the $0$ and $1$ bit are represented by sine waves of $10 \; \mathrm{kHz}$ and $25 \; \mathrm{kHz}$ respectively. These waveforms will be orthogonal for a bit interval of
- $45 \; \mu \mathrm{sec}$
- $200 \; \mu \mathrm{sec}$
- $50 \; \mu \mathrm{sec}$
- $250 \; \mu \mathrm{sec}$