First is to have uniform units.
Conversion factor:
2.54cm = 1in
7cm= 2.76 in
Volume of the paint tray is length times width times height.
V=lwh=10102.76= 275.59 in^3
275.59 in^3 = 4516.12 cm^3 = 4.51612x10^-3 m^3 = 4.51612 L
Conversion factor:
1 gallon = 3.78 L
The volume of the paint tray is 1.19 gallons which is greater than the gallon of paint.