There are advantages<span> to being </span>multicellular<span> rather than unicellular. These include allowing: The organism to be larger. Cell differentiation (having different types of cells with different functions)</span>
Skin is the first line of defense mechanism of our immune system. It acts as a barrier for pathogenic and opportunistic microorganisms. However, skin itself has a microbiota that does not allow other microorganisms to invade or colonize. Any wound, cut or change in the pH of skin due to environmental conditions or any disease might lead to the entry of the opportunistic microorganisms inside the skin. This leads to several skin disorders such as dermatitis, eczema, cellulitis, warts, etc. Thus, it is extremely important to keep the skin hydrated and healthy to avoid any kind of microbial invasion.
There are several information's of immense importance already given in the question. Based on those information's the answer can be easily deduced.
Initial number of bacteria in the culture = 1000
Number of bacteria after t hours = 1000 (2)^t
Then
1000 (2)^t = 50000
2 ^t = 50
t = 5.6
I hope the procedure is clear enough for you to understand.