Miss Croft made snack bags for the picnic that contain three types of snacks: packages of crackers, packages of cookies, and candy bars. A snack bag containing 6 of each type of snack costs $21.00. A snack bag containing 8 packages of crackers, 5 packages of cookies, and 10 candy bars costs $26.00. A snack bag containing 5 packages of crackers, 4 packages of cookies, and 7 candy bars costs $18.50. Solve a system of three linear equations in three variables to determine the cost of one candy bar.