'; (a)
Pattern for the sum of two numbers
Pattern 1: (1 + 0) x 2 + 1 = 3
Pattern 2: (2 + 1) x 2 + 1 = 7
Pattern 3: (3 + 2) x 2 + 1 = 11
Pattern 4: (4 + 3) x 2 + 1 = 15

Formula:
Sum of two numbers = [Pattern Number + (Pattern Number - 1)] x 2 + 1

Sum of numbers in Row 100
= (100 + 99) x 2 + 1
= 199 x 2 + 1
= 399

(b)
Sum of numbers in Row 99
= (99 + 98) x 2 + 1
= 197 x 2 + 1
= 395

Smaller number = 1 u
Larger number = 1 u + 1

1 u + 1 u + 1 = 395
2 u + 1 = 395
2 u = 395 = 1 = 394
1 u = 394 ÷ 2 = 197 (Smaller number)
1 u + 1 = 197 + 1 = 198 (Larger number)

(c)
Remainder 1 = Row A
Remainder 2 = Row B
Remainder 3 = Row C
Remainder 0 = Row D

586 ÷ 4 = 146 r 2

586 will appear in Row B.

Answer(s): (a) 399; (b) 197, 198; (c) B