May someone help me on this

what do u gotta do? pick which ones right

  3 minute    35.969420299997999 seconds

Step-by-step explanation:

Okay in simple words its 3 minute and 35 seconds or something.

Since we want to leave 2 grams ,

Amount to decay = 680-2

                             = 678g

Amount decayed per minute = 27.7 %

Amount decayed per minute ( in grams) = 188.36 g

Amount decayed per second ( in gram ) = 3.139333333g

Your required Ans =  678  /  3.139333333

                               = 215.9694203 seconds

                                i have converted them to minute in the title  : D