massages are sent over a communications channel using two diffrent signals.one signals require 2 micro seconds for transmittal and the other signal requires 3 microseconds for transmittal . each signal of massage is followed immediatly by the next signal.

using the iterative method calcute how many different massages can be sent in 7 microseconds?( s0=1, s1=1, s2=1)

the recurrence relation for "the number of different signal that can be sent in n micrisecond is" ?