Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Driver | Entrant | Constructor | Chassis | Engine | Tyre |
| --- | --- | --- | --- | --- | --- |
| José Froilán González | Scuderia Achille Varzi | Maserati | Maserati 4CLT-48 | Maserati L4s | P |
| Alfredo Piàn | Scuderia Achille Varzi | Maserati | Maserati 4CLT-48 | Maserati L4s | P |
| Johnny Claes | Ecurie Belge | Talbot-Lago | Talbot-Lago T26C | Talbot L6 | D |
| Harry Schell | Horschell Racing Corporation | Cooper | Cooper T12 | JAP V-twin | D |
| Robert Manzon | Equipe Gordini | Simca-Gordini | Simca Gordini T15 | Gordini L4s | E |
| Maurice Trintignant | Equipe Gordini | Simca-Gordini | Simca Gordini T15 | Gordini L4s | E |
| Philippe Étancelin | Private | Talbot-Lago | Talbot-Lago T26C | Talbot L6 | D |
| Louis Rosier | Ecurie Rosier | Talbot-Lago | Talbot-Lago T26C | Talbot L6 | D |
| Charles Pozzi | Ecurie Rosier | Talbot-Lago | Talbot-Lago T26C | Talbot L6 | D |
| Yves Giraud-Cabantous | Automobiles Talbot-Darracq SA | Talbot-Lago | Talbot-Lago T26C | Talbot L6 | D |
| Pierre Levegh | Private | Talbot-Lago | Talbot-Lago T26C | Talbot L6 | D |
| Cuth Harrison | Private | ERA | ERA C | ERA L6s | D |
| Bob Gerard | Private | ERA | ERA A | ERA L6s | D |
| Peter Whitehead | Private | Ferrari | Ferrari 125 | Ferrari V12s | D |
| Giuseppe Farina | SA Alfa Romeo | Alfa Romeo | Alfa Romeo 158 | Alfa Romeo L8s | P |
| Juan Manuel Fangio | SA Alfa Romeo | Alfa Romeo | Alfa Romeo 158 | Alfa Romeo L8s | P |
| Luigi Fagioli | SA Alfa Romeo | Alfa Romeo | Alfa Romeo 158 | Alfa Romeo L8s | P |
| Luigi Villoresi | Scuderia Ferrari | Ferrari | Ferrari 125 | Ferrari V12s | P |
| Alberto Ascari | Scuderia Ferrari | Ferrari | Ferrari 125 | Ferrari V12s | P |
| Raymond Sommer | Scuderia Ferrari | Ferrari | Ferrari 125 | Ferrari V12s | P |
| Franco Rol | Officine Alfieri Maserati | Maserati | Maserati 4CLT-48 | Maserati L4s | P |
| Clemente Biondetti | Scuderia Milano | Maserati | Maserati Milano 4CLT-50 | Maserati L4s | P |
| Louis Chiron | Officine Alfieri Maserati | Maserati | Maserati 4CLT-48 | Maserati L4s | P |
| Prince Bira | Enrico Platé | Maserati | Maserati 4CLT-48 | Maserati L4s | P |
| Toulo de Graffenried | Enrico Platé | Maserati | Maserati 4CLT-48 | Maserati L4s | P |
Question:
what is the engine when the tyre is d, the constructor is era and the driver is bob gerard?
Answer:
ERA L6s