Neco 2021 Civic Education Question 7

A bill was passed by the lower house of the National Assembly with 120 votes in favour. The upper house rejected it. The constitution allows a joint sitting of both houses to reconsider the bill, provided it obtains a two‑thirds majority of the total members present. The lower house has 300 members and the upper house has 150 members. In the joint sitting, all members attend. The 120 lower‑house members who originally supported the bill continue to vote for it, while 80 members of the upper house support it and the remaining 70 oppose it. How many additional lower‑house members must change their vote from ‘against' to ‘for' in order for the bill to achieve the required two‑thirds majority in the joint sitting?