A project requires purchase of plant for 1,000,000 at the start of year 1. The project will last 3 years after which the plant will be sold for 400,000. The plant is assumed to be consumed evenly over the period. The expected profits from the project before deprecation are as follows:

Year 1 400,000; Year 2 700,000; Year 3 600,000; Year 4 0 (break even profit/loss)

What is the accounting rate of return (ARR) for the project (to one decimal place)?

Correct answer is 91.7%, but I don't know how to solve this problem and get 91.7% ARR?