Answer :
2/3 box per 30 secs, multiply by 2 for 1 minute: 2/3 * 2 = 4/3 = 1 1/3
2/3 per 1/2 minute
1/2 times 2=1 minute
2/3 times 2/1=4/3
4/3 box per minute
or 1 and 1/3
1/2 times 2=1 minute
2/3 times 2/1=4/3
4/3 box per minute
or 1 and 1/3