You need to get used to equations of value. Make a time diagram in the form of line graph from 0 to 24 (6 years times 4 quarters). Mark the point zero as the beginning of the 1st year and use that as the comparison date (you could of course use other points from zero to 24 as your comparison date). On one side of an equation write 60,000 as is. One the other side of that equation, write an expression for the present value of the 12 quarterly payments of $4,000 plus an expression for the present value of the 8 unknown R quarterly payments at the beginning of the 5th year (which is the point 16 on your time diagram) which is to be discounted for 4 years (at point 0).