A bar magnet has total length \( 2l = 20 \) units and the field point \( P \) is at a distance \( d = 10 \) units from the centre of the magnet. If the relative uncertainty of length measurement is 1\%, then the uncertainty of the magnetic field at point P is:
 


Rearrange the following parts to form a meaningful and grammatically correct sentence: 
P. a healthy diet and regular exercise 
Q. are important habits 
R. that help maintain good physical and mental health 
S. especially in today's busy world