Figure 1 shows demand (DDD) and supply (SSS) in the market for residential solar panels. Demand is initially at D1 D_1\,D1 and supply at S1S_1S1.
Other things remaining the same, which one of the following combinations of events could have caused demand to shift from D1 D_1\,D1 to D2 D_2\,D2 and supply from S1 S_1\,S1 to S2S_2S2?
A reduction in the price of residential battery storage systems (a complement) and an increase in the wage rates of solar assembly technicians.
An increase in grid electricity tariffs and a technological breakthrough that lowers the manufacture cost of photovoltaic cells.
A rollback of government clean-energy grants for homeowners and a rise in the cost of imported raw silicon.
A fall in grid carbon taxes that lowers retail electricity prices and an improvement in assembly-line automation in solar factories.
