A cash flow profile starts with $2,000 and increases by $1,000 each year up to $21,000 at time 20. Then, it starts again with $21,000 at time 21 and decreases by $1,000 each year to $2,000 at year 40. Convert the cash flow profile to an equivalent gradient series beginning at year ! with $X and continuing through year 40 with $500 increases each year (ending at $X +19,500 at time 40). Interest is 8% compunded annually. Determine the value of X