For the last time Fairfax's appearance in arms helped to shape the future of the country, when George Monck invited him to assist in the operations about to be undertaken against John Lambert's army. In December 1659 he appeared at the head of a body of Yorkshire gentlemen, and such was the influence of Fairfax's name and reputation that 1,200 horse quit Lambert's colours and joined him. This was speedily followed by the breaking up of all Lambert's forces, and that day secured the restoration of the monarchy. For these actions, along with his honourable conduct in the civil war, he was spared from the wave of Royalist retributions. In April 1660 Fairfax was re-elected MP for Yorkshire in the Convention Parliament. He was put at the head of the commission appointed by the House of Commons to wait upon Charles II, at the Hague and urge his speedy return. Fairfax provided the horse on which Charles rode at his coronation. The remaining eleven years of the life of Lord Fairfax were spent in retirement at his seat in Yorkshire. His wife died in 1665 and Fairfax died at Nunappleton in 1671. He was buried at Bilbrough, near York.
Question: How many months after the appearance before the Yorkshire gentlemen was Fairfax re-elected MP for Yorkshire?
Answer: 4