a- Si mezclo 240 ml de agua y 60 de sal, ¿cuánto voy a tener de solución? b- Si quiero obtener 500 gramos de agua salada y tengo 80 gramos de sal, ¿cuánto solvente voy a necesitar? c- ¿cuánto soluto debo colocar en un recipiente que contiene 85 ml de agua, si quiero obtener 100 ml de agua salada?

Astudy by solloch and et. al., in 2017, gives the map above which shows the frequency of alleles with a ccr5-delta32 mutations over 87 different countries. this mutation deletes the presence of a co-receptor (ccr5) on the outside of human t-cells (lymphocytes). some viruses, such as the one responsible for the black death and human immunodeficiency virus (hiv), require this receptor for attachment to host cells during the infection process. the black death was an epidemic that passed over northern europe during the 14th century killing nearly 60% of europeans. according to this information, which explanation best explains why northern europeans show a greater immunity for hiv than some other parts of the world?