Assume that when the price of good X is $10, each, I buy none. When the price is $9 each, I buy 1 per period. When the price is $8 each, I buy 2 per period. When the price is $7 each, I buy 3 per period. When the price is $6 each, I buy 4 per period, and when the price is $5 each, I buy 5 per period. Suppose the seller sets the price at $6 each, and I buy 4 per period. What is the total value to me of the four units?