the nominal rate convertible pthly
the effective annual rate
I assume that "interest at 5% compounded monthly" is american english for "a nominal interest rate of 5% convertible monthly"
The key thing to remember when converting effective rates to nominal rates is:
or, in english
if the nomimal rate (convertible pthly) is x, then the effective pthly rate is x/p
Applying this to part 1:
The effective quarterly rate is supposed to be 6.6/4 = 1.65%
This is an annual effective rate of = 1.067651543
you want to find a monthly nominal rate that has the same annual effective rate
solve for .
can you finish from there? (part 2 requires no new concepts)