AB = √((8-2)² + (9-1)²) = √(36 + 64) = √100 = 10
KL = √((2+2)² + (4-1)²) = √(16+9) = √25 = 5
MN = √((13-4)² + (13-10)²) = √(81 + 9) = √90 = 3√10
PR = √((2+5)² + (-1)²) = √(49 + 1) = √50 = 5√2