For the homework, you were asked to calculate the
signature of a message M3. The first thing to know is
that M3 equals M1 times M2. Substituting M from
here, we can apply the exponent to each determine
the product and we can extend this out applying the
modulus to each product. And M1 to the D power
mod n is signature 1 and M2 to the power of D mod
n is signature 2 and since in our first line, the
signature was taken mod n, you take this mod n and
this is our answer.
