[Grammar] a great amount of effort has been/was put in by ....

[Oceanlike]

I was doing a grammar exercise and came across the question below (a). From the choices available, I chose the answer ‘has been’.
‘Was’ was not among the choices given. I am wondering if there is a difference to the meaning of the sentence if I use ‘was’ instead of ‘has been’

a) A great amount of effort has been put in by the team to prepare for the performance.

Versus

b) A great amount of effort was put in by the team to prepare for the performance.

Thank you for teaching me! :-D

 

[Rover_KE]

a) implies that the effort was made fairly recently and the performance has not taken place yet.

b) means that the effort and performance were in the past.

 

[Matthew Wai]

Having read the above post, I think the following tenses are correct.

a) A great amount of effort has been put in by the team to prepare for the performance that takes place next Sunday.

b) A great amount of effort was put in by the team to prepare for the performance that took place last Sunday.