Answer:
a) El valor de la densidad es 0.79
o 790 
b) El peso especifico es 7749.9
Explanation:
a) La densidad se define como la propiedad que tiene la materia, ya sean sólidos, líquidos o gases, para comprimirse en un espacio determinado. En otras palabras, la densidad es una magnitud que permite medir la cantidad de masa que hay en determinado volumen de una sustancia. Entonces, la expresión para el cálculo de la densidad es el cociente entre la masa de un cuerpo y el volumen que ocupa:

En este caso:
- masa= 237 g= 0,237 kg (siendo 1000 g= 1 kg)
- volumen= 300 cm³= 0,0003 m³ (siendo 1 cm³= 0,000001 m³)
Reemplazando:
→ d=0.79 
→ d=790 
<u><em>El valor de la densidad es 0.79 </em></u>
<u><em> o 790 </em></u>
<u><em></em></u>
b) El peso específico es la relación existente entre el peso y el volumen que ocupa una sustancia en el espacio.
Entonces, en este caso, siendo el peso:
P= m*g= 0,237 kg* 9,81
= 2,32497 N
el peso especifico es calculado como:

Pe= 7749.9
<u><em>El peso especifico es 7749.9</em></u>
<u><em></em></u>
1) See attached figure
The relationship between charge and current is:
where
i is the current
Q is the charge
t is the time
Therefore, the current is the rate of change of the charge passing through a given point over time.
This means that for a graph of charge over time, the current is just equal to the slope of the graph.
For the graph in this problem:
- Between t = 0 and t = 2 s, the slope is

therefore the current is
i = 25 A
- Between t = 2 s and t = 6 s, the slope is

therefore the current is
i = -25 A
- Between t = 6 s and t = 8 s, the slope is

therefore the current is
i = 25 A
The figure attached show these values plotted on a graph.
2)
The previous equation can be rewritten as
This equation is valid if the current is constant: if the current is not constant, then the total charge is simply equal to the area under a current vs time graph.
Here we have the current vs time graph, so we gave to find the area under it.
The area of the first triangle is:

While the area of the second square is

So, the total area (and the total charge) is

I think the answer is letter B