Answer:
7257600
Step-by-step explanation:
Number of freshmen in the student council= 4
Number of sophomores in the student council= 5
Number of juniors in the student council= 6
Number of seniors in the student council= 7
Ways of choosing council members
⁴C₂×⁵C₂×⁶C₂×⁷C₂
⁴C₂×⁵C₂×⁶C₂×⁷C₂=6×10×15×21=18900
Ways of lining up the four classes=4!=1×2×3×4=24
Ways of lining up members of each class=2⁴=2×2×2×2=16
Pictures are possible if each group of classmates stands together
⁴C₂×⁵C₂×⁶C₂×⁷C₂×4!×2⁴
=18900×24×16
=7257600