Determining Spot Rates A three-year, 4%, par-value bond with annual coupons sells for $990$, a two-year, $1000$, 3% bond with annual coupons sells for $988$, and a one-year, zero-coupon, $1000$ bond sells for $974$. Determine the spot rates $r_1$, $r_2$ and $r_3$.
This comes from Mathematical Interest Theory textbook section 8.3 #2. I understand how to compute similar problems, however I am unsure how to solve this given that the bonds have annual coupons(not zero coupon bonds). Any help would be appreciated thank you!

Normally you would start with:
$\frac {40}{1+r_1} +  \frac {40}{(1+r_2)^2} + \frac {1040}{(1+r_3)^3} = 990$
But that is a little messy so make this substitution.
Let $y_1,y_2, y_3 = \frac {1}{1+r_1}, \frac {1}{(1+r_2)^2},\frac {1}{(1+r_3)^3}$
$40y_1 +  40y_2 + 1040y_3= 990\\
30y_1 +  30y_2 + 1030y = 988\\
1000y_1 = 974$
Now you have a system of linear equations, that should be easy enough to solve for $y_1,y_2, y_3.$ From there you can calculate $r_1,r_2, r_3$
