I got this problem here which I can't really solve
A Contractor is given the task of calculating the cost of a tunnel through a hill. The shape of the tunnel's cross section is made up of two curves as shown in the diagram. The upper curve is parabolic while the lower curve is sinusoidal (half cycle of sine curve 2 m deep). The tunnel is 10 m wide 6 m high at the wiedest points as shown in the diagram.
The Task: Given that the tunnel is 1.25 km long and cast $120/m^3 to excavate, estimate the cost of excavation to the nearest $ 1000.
Thanks in advance