day 74 was supposed to be an "AND" , someone made it a "OR" ( tyvm )
day 75 ... is 1 of the easiest tasks....
if you're an established player, yes easiest is (2) marble to lvl-5.
I suggest for this option, just waste 2x2 for the event, and keep (2) marble
@ lvl-4 @ all times... hit this task, its an easy upgrade to lvl-5, and quick.
As soon as they finish, sell them and replace with lvl-4's again.
if you're not advanced, like CH 1-3 , then I suggest using residences...
ya have (2) lvl-5 , and (2) lvl-4 .... since going negative in population
is no big issue for short periods of time...... when you hit that task, then
you just sell the lvl-5's, upgrade the lvl-4's -> lvl 5, and start the lvl-4 replacements.
Doing either of these 2 options, on 24 hr locked tasks, is easy-peasy and requires
absolutely 0 scouts or time boosters. ( even if there's 3 of them in a row )