Find the volume of a rectangular pipe 1 m long if its outer are of cross-section is 4 cm x 3 cm. But its internal area of cross-section is 3.5 cm x 2.5 cm. Help me ASAP. TY

Area of cross section of outer portion of pipe = $4 \mathrm{cm}\times 3 \mathrm{cm} = 12 {\mathrm{cm}}^2$
And area of internal cross section of pipe = $3.5 \mathrm{cm}\times 2.5 \mathrm{cm} = 8.75 {\mathrm{cm}}^2$
Height of rectangular pipe = 1 m = 100 cm
So, volume of outer portion of rectangular pipe = $12\times 100 = 1200 {\mathrm{cm}}^3$
And volume of internal portion of pipe = $8.75\times 100 = 875 {\mathrm{cm}}^3$
So, volume of a rectangular pipe = $1200 {\mathrm{cm}}^3-875 {\mathrm{cm}}^3 = 325 {\mathrm{cm}}^3$
Therefore volume of rectangular pipe is 325${\mathrm{cm}}^3$.