Answer:
I would say there would be 5-10% in a city, and maybe 10-20% in the country. It mainly varies depending on how big the city is, how many people/districts there are, and the size of the country, which makes it hard to give a certain percent of shops, as there may be small businesses included as well or new shops being built. 
Hope this helps! This was pretty confusing for me as well so i hope the answer is alright (×﹏×)
 
        
             
        
        
        
One mole of a substance contains 6.02 × 10∧23 particles. Thus we first convert  89.2 g to moles. 1 mole of sodium contains 23 g
Hence 89.2 g = 89.2 / 23 g = 3.878 moles
Therefore, 3.878 × 6.02×10∧23 particles= 23.346 × 10∧23 particles
Hence 89.2 g of sodium contains 2.335 ×10∧24 particles 
        
             
        
        
        
3 moles of oxygen will react with 1 mole of ethylene. Convert 12.9 L of oxygen to x moles of oxygen, then divide by three.
        
                    
             
        
        
        
When Ka =1.37 x 10^-4 
∴Pka = - ㏒Ka
          = -㏒ 1.37 x 10^-4 
          
           = 3.86
According to H- H equation: 
when PH = PKA + ㏒[conjugate base / weak acid]
when the lactate is the conjugate base and lactic acid is the weak acid 
∴ PH = Pka +㏒[lactate] / [lactic acid]
so, by substitution:
4.49 = 3.86 + ㏒[lactate]/[lactic acid]
∴[lactate]/[lactic acid] = 4.3
∴ [lactic acid] / [lactate] = 1/4.3 
            
                                        = 0.23