Set up the equation: [ 60,000 = \frac{20,000}{(1 IRR)} \frac{20,000}{(1 IRR)^2} \frac{20,000}{(1 IRR)^3} \frac{20,000}{(1 IRR)^4} ] Simplify the equation: [ 60,000 = 20,000 \left( \frac{1}{(1 IRR)} \frac{1}{(1 IRR)^2} \frac{1}{(1 IRR)^3} \frac{1}{(1 IRR)^4} ight) ] Divide both sides by 20,000: [ 3 = \frac{1}{(1 IRR)} \frac{1}{(1 IRR)^2} \frac{1}{(1 IRR)^3} \frac{1}{(1 IRR)^4} ]