(b) 26 units
By Pythagoras theorem, we find that the given triangle is a right angled triangle with 12 as height and 5 as base.
∴ Area of the triangle = \(\frac12\) x 12 x 5 sq. units = 30 sq. units
∴ Area of the rectangle = length × breadth = 30
⇒ Length = \(\frac{30}{breadth}=\frac{30}{10}\)= 3 units
∴ Perimeter of the rectangle = 2 × (10 + 3) units = 26 units.