The units digit of Quantity A is 9.
The units digit of Quantity B is 1 (the units digit of 81).
Therefore, Quantity B is greater than Quantity A.
Quantity A:
The units digit of 13 is 3.
The units digit of powers of 3 follow a cycle of 4: {3, 9, 7, 1}.
Since 13 is odd, 13¹³ will also have the same units digit as 3¹³.
Therefore, the units digit of 13 × 13¹³ is the product of the units digits of 3 and 3¹³, which is 3 * 3 = 9.
Quantity B:
The units digit of 19 is 9.
Similar to Quantity A, the units digit of powers of 9 follow a cycle of 2: {9, 1}.
Since 19 is odd, 19¹⁹ will also have the same units digit as 9¹⁹.
Therefore, the units digit of 19 × 19¹⁹ is the product of the units digits of 9 and 9¹⁹, which is 9 * 9 = 81.