4. A parallelogram \(A B C D\) has area \(40 \mathrm {~cm} ^ { 2 }\)
Given that \(A B\) has length \(10 \mathrm {~cm} , B C\) has length 6 cm and angle \(D A B\) is obtuse, find
- the size of angle \(D A B\), in degrees, to 2 decimal places,
- the length of diagonal \(B D\), in cm , to one decimal place.