Since,\( \Large AC^{2}=AB^{2}+BC^{2} \)

=> \( \Large (25)^{2}=(15)^{2}+(20)^{2} \)

=> 625=225+400

=> 625 = 625

So, the triangular field is right angled at B

Area of the field = \( \Large \frac{1}{2}\times AB\times BC \)

= \( \Large \frac{1}{2}\times 15\times 20 \)

=\( \Large 150m^{2} \)

So, the cost of sowing seed is RS. 5 per sq m

Cost of sowing seed for

\( \Large 150m^{2}=150\times 5 \)

= RS. 750