Party A and Party B cooperate for 4 hours * * * to complete 25% of the total task, namely 1/4,

Then Party A and Party B cooperate to complete 25% of the total task per hour ÷ 4 =116.

Later, B worked alone for 8 hours and A worked alone for 20 hours, which can be regarded as 8 hours of cooperation between Party A and Party B,

Then A does it alone for 20-8= 12 hours,

Then Party A and Party B cooperate for another 8 hours to complete 25% of the total task × 2 =1/2.

At this time, there are 1-25% tasks -( 1/2) = 25%.

It takes one person 12 hours to complete.

Then A completes 25% per hour12 =1/48.

∴a It takes 1÷( 1/48)=48 hours to do it alone.

[(1/4)-(1/48) × 4] ÷ 4 = 1/24 of the total tasks per hour.

It takes 1÷( 1/24)=24 hours for a person to do this.