The frictionless track for a toy car includes a loop$-$the$-$loop of radius $R.$ From which minimum high, measured from the bottom of the loop, must the car be placed to start from rest on the approaching section of track and go all the way around the loop?

$($a$)y_1>2\frac{R}{2}$

$($b$)y_1<mn>5</mn><mfrac><mrow><mi>R</mi></mrow><mrow><mn>2</mn></mrow></mfrac>$

$($c$)y_1=2\frac{R}{5}$

$($d$)y_1=5\frac{R}{2}$

$($e$)y_1=5R$