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To start with, we have the length of the semicircular tunnel, \[l\]= 2 km = 2000 m.

The diameter of the semicircular tunnel = 7 m.

Now, radius of tunnel = \[\dfrac{7}{2}\] m = 3.5 m

So, r = 3.5 m, \[l\]= 2000 m,

Volume of semicircular tunnel, which should be half of the volume of the circular tunnel,

= \[\dfrac{1}{2} \times \]volume of circular tunnel

= \[\dfrac{1}{2} \times \]\[{\pi }{{\text{r}}^{\text{2}}}{\text{l}}\]

= \[\dfrac{1}{2} \times \]\[\dfrac{{22}}{7} \times 3.5 \times 3.5 \times 2000\]

= \[11 \times 0.5 \times 3.5 \times 2000\]

= \[38500{m^3}\]

So, expenditure for digging (semicircular) the tunnel at the rate Rs. 600 per \[{m^3}\],

= \[38500 \times 600\]

= Rs. \[2,31,00,000\]

Now, for the expenditure for plastering the inner side of the tunnel at the rate Rs. 50 per \[{m^2}\],

The inner area of the tunnel = \[{\pi rl}\]

So, if we calculate, And inner area of the tunnel = \[{\pi rl}\]= \[\dfrac{{22}}{7} \times 3.5 \times 2000\]= 22000 \[{m^2}\]

So total expenditure = 22000\[ \times \]50

= Rs 11,00,000