Let the number of shirts of brand B be x.
Let the cost of a shirt of brand B be rs 1.
$\therefore$ Original cost = 4 × 2 + x = rs (8 + x)
In case II,
4+2x = $(8+x)\times\frac{140}{100}$
=> 20 + 10x = 56 + 7x
=> 10x – 7x = 56 – 20 = 36
=> 3x = 36
=> x = 12
$\therefore$ Required ratio = 4 : 12 = 1 : 3