synchronous data transfer

Question

A synchronous transmission T has transfer rate of 100 char/ sec. If T uses some synchronous characters followed by some 8 bit info characters, what is the total number of synchronous bits required where bit rate is 1000 bits/ sec?

Answer 1

T is transferring 100 char/sec 800 bits/sec as one char needs 1 Byte.
bit rate is 1000 bits/sec it means along with 800 bits of data, 200 bits are used for synchronization.  
total 100 characters are sent using 200 synchronous bits. It means each character will be followed by 1 start bit and 1 stop bit. total 10 bits will be sent for 1 char.

Answer 2

let x extra bits are required,

efficiency= $\frac{8}{8+x}$

effective bandwidth=efficiency*total bandwidth=1000*$\frac{8}{8+x}$

given effective rate=100char/s=800bits/s

therefore 1000*$\frac{8}{8+x}$ =800

x=2

therefore in order to transfer one char(8 bits), 2 extra synchronous bits are required..