Answer:
potential energy is maximum when streach distance of string is doubled
Step-by-step explanation:
we know that elastic potential energy of a spring is given as
..................(1)
here k is spring constant
and x is stretched distance of spring
if we double the spring constant then potential energy will be given as

...............(2)
similarly if we double the stretch distance then potential energy in spring will be given as

.............(3)
from equation 2 and equation 3 it is clear that

it means potential energy is maximum when stretch distance of string is doubled