The beam under consideration is a simply supported rectangular cross$-$section beam with a safety classification of II$.$ Its cross$-$sectional dimensions are $bxh=200mm400mm.$ The calculated length is $1_0=5\mathrm{.}00m($used to calculate the bending moment$),$ while the net length is $1_n=4\mathrm{.}86m($used to calculate the shear force$).$ Two linear loads act on the beam: a permanent load with a characteristic value of $10k\frac{N}{m}($excluding self$-$weight$)$ and a variable load with a characteristic value of $7k\frac{N}{m}.$ Additionally, there is a variable point force applied at the mid$-$span with a characteristic value of $20kN.$ calculate the basic combination for obtaining maximum bending moment at midspan and maximum shear force at the support edge. $($note: the design working life is $100$ year, and the combination coefficient is $0\mathrm{.}7)(25\text{'})$