How long will it take to do this?

Students: Print this page - then write your name at the top. The 
numbers in the bottom row and in the right most column are the 
totals for the columns, rows and the left-to-right, top-to-bottom 
diagonal - they are shown in bold type. The block of numbers has 
some numbers missing - see the empty boxes. Fill in those numbers so 
that the totals for all rows, columns and the left-to-right, top-to-
bottom diagonal match the totals shown.