According to Kepler's Third Law – The Law of Periods,
T2∝R3
where T is time taken by the planet to go once around the sun and R is the semi-major axis (distance) of the elliptical orbit.
∴T2=kR3…(i)
Where k is a constant of proportionality.
When R becomes 3 times, let the time period be (T′).
∴(T′)2=k(3R)3…(ii)
∴(T′)2T2=271
So, time period will be 33yr.