Took my time (around 10 mins) and got 8/9 Decided to make a new try selecting randomly (around 10 seconds) and got 4/9. Old lesson from engineering school remin

Took my time (around 10 mins) and got 8/9 Decided to make a new try selecting randomly (around 10 seconds) and got 4/9. Old lesson from engineering school reminded: usually the most accurate is not the most cost effective solution.