7. 10.7 A website determines how many dollars today have the same buying power as a stated amount of money at the beginning of any year in the past. When the values 1920, 2019, and $1000 are entered for the beginning of the initial year, beginning of the desired year, and initial amount, respectively, the result is $12,831. On the basis of these numbers, what was the average annual inflation rate between 1920 and the end of 2018? Solve by

(a) equation, and

(b) spreadsheet using GOAL SEEK.