[填空题]
The following diagram shobqd * b 9h:lye8n2ep5sws the parabolic shape of a gab4w ) ;41.0u a dkj3maguwvizfteway arch that has a span of 12 metres and a maximum heighg34zmk.u;a4wi0 b)jd u1fw avt of 8 metres.
The curve has an equation in the form y=$k(x-6)^{2}+8$ .
1. Determine the value of k is $\frac{a}{b}$;a= ,b= .
2. Write down an integral that represents the cross sectional area under the arch shown as OMN.
A=$\int_{0}^{12}\left[-\frac{a}{b}(x-6)^{2}+c\right] \mathrm{d} x$;a= ,b= ,c=
3. Find the cross sectional area under the arch.Evaluating the integral in part (b), we get a= m$^2$.
